Water-soluble cationic polymers, such as copolymers of acrylamide and a cationic monomer, e.g., dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, or a quaternary salt thereof, are very useful as high molecular weight polymer flocculating agents, high molecular weight polymer dehydrating agents, paper manufacturing chemicals, etc.
A W/O emulsion and a process for producing the same are disclosed in JP-B-34-10644 (the term "JP-B" as used herein means an "examined published Japanese patent application") by Banderhoff, et al. However, since the disclosed emulsion is not stable in practice, it has been required for economical use that the water-soluble polymer should be separated from the emulsion by sedimentation and recovered as a solid.
Some of the defects of the emulsion of Banderhoff, et al. were overcome by U.S. Pat. No. 3,624,019 to Anderson et al., in which a polymer does not need to be isolated as a solid. The emulsion of the Anderson patent contains a surface active agent whereby the emulsion will be inverted to an aqueous polymer solution on addition to water. Although the W/O emulsion of Anderson et al. brought about an advance in the conventional process for production and the method of use, the capability of inversion of the surface active agent used in the emulsion is still insufficient because a long time is required for inversion and/or a large addition of the surface active agent is required to accomplish inversion within a predetermined time.